The objective of this work is to investigate genetic redundancy and its possible roles in the development of higher organisms. Specifically the regulation of ribosomal-DNA quantities and RNA transcription rates will be studied using the techniques of molecular hybridization and molecular biology. Chromosomal aberrations in Zea mays and Crepis species hybrids, analyzed cytogenetically, will serve as a source of genetic variation for some of the biochemical tests to be performed. Preliminary experiments indicate a regulation of ribosomal-DNA amounts (i.e. number of redundant genes) in certain genetic conditions. Another line of study will involve determination of differences in nucleic acid content between heterochromatin and euchromatin using stocks of Zea mays that differ significantly in the amount of heterochromatin.